Computer Aided Stress Modeling for Optimizing Plastic Package Reliability

A computer-aided stress analysis program has been applied to reliability prediction of VLSI plastic packages. The process of plastic encapsulation and the testing by temperature cycling produce stresses in the silicon chip as well as in the molding material. These stresses must be minimized through specific choices of material and package design. Finite element stress modeling is used to quantify and display the effect of material choices, form factors, and innovative processing techniques. Excellent correlations have been achieved between the model predictions and the actually observed failures and quantitative stress measurements using strain gauge test structures. The mechanical and thermal problems associated with VLSI assembly and packaging can then be minimized.